This has been the arena since.
4 seconds sound clip from the Duel to the Death movie soundboard.
You can hear this line at 00:44:11 in the Blu-ray version of the movie.
Quote context
[...]
- It's been a long time since we've had guests here. I am happy you came. It's been much too quiet.
- We should take them to look at the rock.
- Think of all the warriors who have fought this duel. You'll find every name on these walls.
- Why is every duel fought here? Is there a special reason?
- This has been the arena since.
- You should be grateful. Few have seen this place.
- You are lucky and you are both so young. Indeed, you may be the youngest ever.
- It's a shame. Many fighters, they dream of dueling here. But we have to turn them away.
[...]